Switch from AGM to FLA batteries

[Utahsailor]

This forum has been my best source for installing solar panels and I expect it will be for a question on switching from AGM to FLA in my house bank. This question has undoubtedly been answered before but I couldn’t find it. Improper storage, mis-measurement and an amperage leak have croaked my 840 AHr house bank. I plan to increase to 6 4D batteries for about 1,200 AHr

Charging sources are: 310 A from main engine through 2 Balmar alternators, 90 A from Zantrex invertor/charger and output from 840 WHr solar panels through dual PPM controllers (max about 35 A). Since the alternators very quickly fall below 120 A, the maximum charge rate will be less than .1C.

I would like to replace with FLA but have these questions:

1. Will outgassing be a problem with this low charge rate? (If so, what’s best way to vent the gasses? The engine has a powerful bilge blower that is always on while engine is running.)
2. Why do so many use 6V instead of 12V? Replacing with 4D FLAs gives 200 AHr at $235 each and allows reuse of existing cables.


Thanks for the advice

[kentobin]

As to using 6 volt vs 12 volt batteries: Each 6 volt weighed in at 63 lbs. Each 12 volt 4D I removed weighed in at 134 lbs. I was able to hand carry the 6 volts down the companionway. Needed a block and tackle attached to the boom to get the 4d out of the salon hatch.

Then there was availabilty and cost. The 6 volts were available at a local Costco the 4D would have to be ordered and were much more expensive than than the $200 I paid for the two 6 volt golf cart batteries. It's been over 3 years since I researched this and I have no recollection of the 4D price just way more.

One of the banks needed rewiring as either the negative or positive post wouldn't reach the existing run. The other bank was good. I don't remember the cost.

I've had no problem with outgassing and the batteries are under the seating in the salon. Not a very scientific study.

Most important with flooded batteries is that you have easy access for checking the fluid levels in the batteries.

A friend of mine is a small boat marine surveyor and swears by Concorde AGM batteries. Kind of pricey for my taste. He says he's seen them repeatedly run flat and recharged with no reduction in battery life.

[transmitterdan]

Originally Posted by Utahsailor

Improper storage, mis-measurement and an amperage leak have croaked my 840 AHr house bank. I plan to increase to 6 4D batteries for about 1,200 AHr

I don't understand how your AGMs got "croaked" but it sounds like you could have too much AH storage and not enough charging. You may be trying to run for many days without charging but not putting AGMs up to full charge regularly is a good way to kill them. Adding additional AH capacity but not increasing charging capacity seems to be going the wrong way. I suspect your batteries may last longer if you reduce the AH capacity to something like 600AH.

6V batteries are a lot lighter and easier to handle than 4Ds.

[Stu Jackson]

4Ds are not true deep cycle batteries. They are "dual purpose" and fit for neither. Save your back, get 12V or 6V.

As far as ventilation is concerned: it is good, but gassing hasn't been a problem for hundreds of thousands of boaters for years and years. In many cases, one can add simple louvres to battery compartments, but in reality so many battery enclosures already have openings. For the cables. Think about it...

Good luck.

[wrwakefield]

Originally Posted by Utahsailor

This forum has been my best source for installing solar panels and I expect it will be for a question on switching from AGM to FLA in my house bank. This question has undoubtedly been answered before but I couldn’t find it. Improper storage, mis-measurement and an amperage leak have croaked my 840 AHr house bank. I plan to increase to 6 4D batteries for about 1,200 AHr

Charging sources are: 310 A from main engine through 2 Balmar alternators, 90 A from Zantrex invertor/charger and output from 840 WHr solar panels through dual PPM controllers (max about 35 A). Since the alternators very quickly fall below 120 A, the maximum charge rate will be less than .1C.

I would like to replace with FLA but have these questions:

1. Will outgassing be a problem with this low charge rate? (If so, what’s best way to vent the gasses? The engine has a powerful bilge blower that is always on while engine is running.)
2. Why do so many use 6V instead of 12V? Replacing with 4D FLAs gives 200 AHr at $235 each and allows reuse of existing cables.


Thanks for the advice

We changed out our battery bank last year and were faced with similar decisions: replace the FLA with AGM, or keep FLA. We went through the same analysis you are, and decided to stay with FLA for a variety of reasons. [See our blog post for details if interested.]

RE: Outgassing: Remember AGMs can outgas as well, just not as much... With FLAs our outgassing is trivial during normal charging, but extreme during equalization cycles. [Which are very necessary for longevity of the battery bank...] Our decision to stay with FLA was made easier by the previous owner's installation of an enclosed battery compartment that vents outside the boat.

A corollary consideration to FLAs is watering. In our blog post we discuss an centralized system we installed (and love...) which was necessary due to the remote location of our bank...

And speaking of battery location, you mentioned engine room blower to assist with venting batteries. If you bank is in a warmer than ambient area [our engine room holds a consistent 115F when we are motoring for long periods] that will reduce battery life over time, and also reduce the charging regimen accordingly [hence why the 'smart' chargers and regulators have battery temp {and alternator temp} sensors as an option...]

RE: 6 VDC vs. 12 VDC batteries [parallel and series wired to produce desired voltage]: one answer is you can reduce both weight and volume (reduce both by ~ 1/3rd) of the battery bank and still achieve your target AH capacity. In your case [depending upon the design of your existing battery compartment] you might be able to replace each 4D with 3- GC2 sized [typical size...] 6VDC batteries @ 200+ AH/pair. [to achieve 12 VDC] This means with 12- 6VDC batts you could achieve the AH capacity you are looking for using only 2/3rds of the space [and weight...] for batts you use with 4D.

Another reason many choose 6VDC batteries is they are purpose made for deep cycle and historically last a bit longer if well cared for. [Not to mention relative ease of handling vs. 4D...]

Have fun re-evaluating the engineering of your battery bank.

[Reichberger]

Hi Utahsailor,


It would be prudent before you go to greater expense and work to pay $19.99 at the site www,morganscloud.com (Attainable Venture Cruising site) and read the online booklet: "Battery Installation & Maintenance". It will explain all your problems.


The larger the Banks' amp-hr capacity the better. 'Trojan' deep cycle (golf cart type) batteries are the way to go. The Pro's and Cons of battery types, weights, sizes, charging arrangement are all in Boatowners Mechanical & Electrical Manual EdIII by Nigel Calder. You can pick this book up from Amazon for a few dollars second hand.


I wish you all the best, Erich

[leftbrainstuff]

Originally Posted by Utahsailor

This forum has been my best source for installing solar panels and I expect it will be for a question on switching from AGM to FLA in my house bank. This question has undoubtedly been answered before but I couldn’t find it. Improper storage, mis-measurement and an amperage leak have croaked my 840 AHr house bank. I plan to increase to 6 4D batteries for about 1,200 AHr

Charging sources are: 310 A from main engine through 2 Balmar alternators, 90 A from Zantrex invertor/charger and output from 840 WHr solar panels through dual PPM controllers (max about 35 A). Since the alternators very quickly fall below 120 A, the maximum charge rate will be less than .1C.

I would like to replace with FLA but have these questions:

1.Will outgassing be a problem with this low charge rate? (If so, what’s best way to vent the gasses? The engine has a powerful bilge blower that is always on while engine is running.)
2.Why do so many use 6V instead of 12V? Replacing with 4D FLAs gives 200 AHr at $235 each and allows reuse of existing cables.


Thanks for the advice

We run 6 x 6V Trojan T105s. They are now 8 yrs old and still in good condition. They consume more water as they get older but this is normal. They are purpose built for deep cycle use and can be hand carried. Outgassing is not an issue. We use a syringe and tube to fill using the Trojan remote fill caps with the level indicator.

We have 130A Balmar alternators and xantrex 3 stage regulators for both engine and generator.

We have 280W solar and wind. We use a heart interface as our primary battery management system.

Starting and winching batteries are a completely seperate charging and regulation circuit.

System sizing to these rules maximises battery longevity:

1) ensure your draw aligns with no more than 30% of your Ahr capacity for FLA.
2) size your max solar to get you to full charge each day.
3) FLA like to be fully charged all the time. 50 - 80% is easy. The last 20% is more challenging but where you maximise your battery life.
4) keep the water levels up
5) size your alternators to give you a net charge increase for typical necessary engine use. Not necessarily the largest Amps.
6) use 3 stage chargers with closed loop temp control. Batteries are sensitive to temp which correlates with life.
7) size cables appropriately. Never scrimp. Ever.
8) keep everything clean. Spotless.
9) monitor and log your draw, water consumption and the contributions of all systems that draw and charge. This will highlight what works well and give early warning of issues.
10) before you think coffee in the morning check your batteries. We start the day with 'how is system X', then we ask 'coffee...'.

Good battery management is both art and science.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[Utahsailor]

Excellent advice, thank you all. With the input, I have chosen Trojan T105s and will fabricate a new battery box and add buss bars to keep everything organized. I'll try to document the change over and post back to forum.

Utahsailor

[Utahsailor]

Leftbrainstuff: Nice battery check list. We tend to run the engine early while we brew coffee, the sun is low and the batteries are at their most discharged, so maximum current will flow to them and ensure that we get into float with the solar panels.

Utahsailor